The present invention relates to a balance with a balance housing containing a weighing cell and with a carrier for the weighing load.
Balances of this type serve mainly as analytical balances and are used widely in laboratories.
A balance meeting the foregoing description is disclosed in U.S. Pat. No. 4,766,965. The weighing pan is supported by a cantilever arm that is attached to and projects forward from the bottom end of the load receiver of the weighing cell. The weighing pan is arranged immediately above the floor of the weighing compartment and is connected to the cantilever arm through an opening in the floor. A calibration device with a mechanism for raising and lowering the reference weights is arranged below the floor of the weighing compartment.
A further balance in the same general category is described in JP 62-266421, disclosing a concept where the weighing pan as well as a cantilever arm supporting the weighing pan are arranged above the floor of the weighing compartment. The support arm for the weighing pan is connected to the inner working mechanism of the balance through a passage opening in the rear wall of the weighing compartment.
The object of the present invention is to propose a balance that has a compact design, does not easily become contaminated and can be used in a multitude of applications.
A balance according to the present invention has a balance housing containing a weighing cell. The weighing-load carrier of the balance is configured as a plane horizontal grate (synonymously referred to as a level grate).
This has many possible applications for weighing in a laboratory. For example, receptacles or devices of the most diverse kinds can be set on the grate and/or clamped to the grate. Spilled sample material does not stay on the weighing-load carrier but drops off between the bars of the grate, so that the spilled material cannot inadvertently be included in a weighing.
It is advantageous to arrange a fixed or removable spill-collector pan on the floor of the weighing compartment to catch spilled weighing sample material. This greatly facilitates cleaning of the weighing compartment.
In a particularly favorable design, the bars of the grate have a roof-like triangular profile with a ridge at the top, which further reduces the risk that spilled sample material could falsify the weight measurements. Using a grate as weighing-load receiver has also particular advantages for fastening different kinds of holders for sample containers.
In a preferred embodiment of the invention, a load-relief mechanism is arranged at the rear wall for raising and lowering the load on the weighing-load carrier. The load-relief mechanism has a lift platform shaped like a grid of bars or spaced-apart lamellae. When the lift platform is raised, the bars or lamellae of the lift platform come up through the gaps between the bars of the carrier grate for the weighing load and lift the weighing object off the carrier grate. This process serves to automate the tare function. With the load-relief mechanism, it is not necessary to remove and subsequently return the weighing load when re-zeroing the balance. Thus, a potential source of weighing errors is avoided. It is also possible to perform long-term weight studies and recalibrate the balance between the individual weighings.
To facilitate cleaning of the balance, the lift platform is designed to be easily disassembled. Preferably, the load-relief mechanism is motorized.
Advantageous traits of a balance according to the invention are its compact design and its modular configuration that make it remarkably versatile for a variety of laboratory applications. The inventive balance is distinguished by its flexibility and by how quickly it can be reconfigured for different applications. In addition, cleaning the separate components is very easy.